Nonreturn valves, or check valves, are used in a variety of applications for establishing unidirectional flow. For example, the fuel delivery system of a gas turbine can have a nonreturn valve which ensures that fuel exits the fuel supply system when the fuel has been pressurized to a threshold level. The nonreturn valve opens when the fuel pressure has reached the threshold level and closes when the fuel pressure drops below the threshold level.
Gas turbines can be operated at a high temperature level, and the heated fuel can cause coking throughout the turbine, including the fuel delivery system. Coking results when fuel stagnates in certain locations of the fuel delivery system, such as in corners. The stagnated fuel can solidify in place as it continues to be heated.
Coking and other deposits can cause the nonreturn valve to seize closed or open. Known methods for releasing seized nonreturn valves in gas turbines involve breaking the flow path at the point where the seizure has occurred and manually resetting the valve to an operational condition. However, in a device which may have several operational cycles before coming offline, manually resetting valves can be impractical.